OT Military multi-fuel engine

The thread on gas in the diesel fuel sparked my memory on these engines. Just wondering if anyone knows what goes on in what is basically a diesel engine(22 to 1 compression, if I remember right) that allows it to burn gasoline as well? I know there is some kind of fuel density compensator, but I have no idea on what it does, or how one ignites gas using just compression without serious pre-ignition problems? Any info would be good.

I can't answer specific questions on your multi-fuel military diesel, but pre-ignition is not a factor in a diesel because the fuel is not admitted to the heated compressed air until combustion is desired.

My understanding is that diesel engines could run off of gasoline, if you could easily pump it to the pressure required to direct inject it into a diesel. Diesels running off of petroleum diesel fuel get lubricity from the fuel to lubricate the high pressure pump.

There might be other reasons diesel engines are not fueled with gasoline, but gasoline having no lubricity for the injection pump has historically been one factor. I remember reading some time ago about a direct injected experimental diesel running on gasoline using an injection pump with ceramic parts. I have never read anything more about running diesels on gasoline, except I've also heard of the military multi-fuel diesel engine and I'm also curious as to how they operate. Maybe you mix some oil in the gasoline?

Sorry I could not answer you question, but I'm also curious so I thought I'd throw my two cents in.

Only things I am aware of as factors on the military multi-fuels is that they run BEST on diesel or jet fuel (pretty much the same things). They CAN run on alcohol, gasoline, or pretty much anything else liquid that will burn, but I do not know what the consequences are. Being military, service due to damage from running on a secondary fuel would be acceptable, given the need to do it... In other words, if running 48hrs on gasoline ruins the fuel pump and injectors, but gets the troops out of harm's way, or gets supplies to a unit in need, that is a perfectly acceptable consequence. Just swap those parts out and keep going. Probably why we don't have multi fuel engines in civillian service.

I googled military multifuel engines and this is all I found. This was in a forum, so investigate before believing it.

The secret is a special type of injector that sprays instead of fogs, along with a cupped piston that swirls the fuel with a compression ratio of 22 to 1 , and a fuel density compensator in the back of the injector pump that plays a major part in the working.

You might check on an ANGIQUE TRACTOR website as there were old tractors made that would run on eitiher gas or kerosene---some would start with gas and by turning or flipping a switch they ran on the kerosene.

Here is a site that will tell you all you ever wanted to know about the multi fuel engines. These guys will run them on dam near anything including 100% pre filtered waste oil!Steel Soldiers::Military Vehicles Supersite

multi fuel Studebaker

I had a Studebaker pickup I ran on #2 fuel oil during a time of extreme poverty. It was not happy, but it ran. Lots of blue smoke, knocking on acceleration, and hard starting. If it had not been a hot July and a low compression flathead engine, the attempt would have failed dismally.

If you ask me its sort of a slug...427cid, 1500lb and produces 140bhp...with a turbo!!!

Granted its probably a 3" bore and 7" stroke for a fat torque curve but its giving away a lot of efficiency for the ability to burn multi-fuels IMHO.

There are also early Farmall tractor diesel engines (Super M era, IIRC) which start on gasoline and then switch to diesel operation via operator intervention. Again its prechamber and not much compression.

Thanks for the info and the links. The Pop. Mech. site was basic, but it does explain a little bit more than I knew before. The Steel Soldiers site has more than enough info on anything I could think of, but will take a long time to digest all of it!

The military multi-fuel trucks include the 2 1/2 ton and 5 ton. The engines were manufactured by Continental and White. The design and license of the engines came from the German firm, MAN. It was called the "MAN Hypercycle Engine". As noted previously, the design relied upon a fuel density compensator, a spray-type injector, a deep cupped piston that helped retard the ignition of the higher octane fuels, and an lube oil spray nozzle that bathed the underside of the piston. To minimize maintenance and improve performance, most operators have bypassed the compensator and only burn diesel fuel. The current generation of military trucks are designed to burn only military diesel fuel, (JP-8). Regards, Clark